From Forum Nokia Wiki
On Nokia mobile phones, you can key in certain codes in standby mode that will display information or make the phone perform certain operations. This is a reference of such codes.
Note that not all codes apply to all phone models
- "*#0000#" - displays firmware version (and date) and phone model
- "*3370#" - activates Enhanced Full Rate Codec (EFR); better sound quality for slightly reduced talk time
- "#3370#" - deactivates Enhanced Full Rate Codec
- "*#4720#" - activates Half Rate Codec; worse sound quality for better talk time. Same code deactivates it
- "*#9999#" - displays firmware version if *#0000# doesn't work; only works on some models
- "*#2640#" - displays phone security code
- "*#7780#" - restore factory settings
- "*#92702689#" - displays total duration of phone calls
- "*#43#" - check the "Call Waiting" status
- "*#61#" - check the number that "On No Reply" calls are diverted to
- "*#62#" - check the number that "Divert If Unreachable (no service)" calls are diverted to
- "*#67#" - check the number that "On Busy Calls" are diverted to
- "**21*number#" - turn on "All Calls" diverting to the phone number entered
- "**61*number#" - turn on "No Reply" diverting to the phone number entered
- "**67*number#" - turn on "On Busy" diverting to the phone number entered
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